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Hypophosphataemia - how to treat

MEDICINES INFORMATIONFREQUENTLY ASKED QUESTION

Question:

How to treat hypophosphataemia in adults

Background:

Most of the phosphorus present in the body is contained in bone and the remainder is predominantly intracellular. It is therefore difficult to assess total body stores from serum phosphate levels. Symptoms of phosphate depletion are uncommon but those attributed to the disorder include muscle weakness, anorexia, paraesthesia, seizures and haemolytic anaemia. Severe phosphate depletion can result in encephalopathy, coma and death. The most common causes of acute hypophosphataemia are treated diabetic ketoacidosis, re-fed alcoholics, severe burns and respiratory alkalosis and in these it occurs because phosphate is redistributed in cells. The cause of hypophosphataemia and whether or not it is due to phosphate depletion must be established before initiating phosphate replacement therapy. Phosphate depleting drug therapy, such as phosphate-binding antacids and diuretics, should also be withdrawn where possible.

Reference range 0.8-1.5mmol/L.

xxx

Mild

0.65 - 0.79mmols/L

Moderate

0.32 - 0.64mmols/L

Severe

<0.32mmols/L

Answer:

Specific treatment depends on the presence of symptoms as well as on the anticipated duration and severity of hypophosphataemia.

Oral supplements are often poorly tolerated due to diarrhoea, if this occurs dose should be reduced.

The tablets should be administered with plenty of water, this can help to avoid diarrhoea.

Note: tablets also contain 20.4mmol sodium and 3.1mmol of potassium per tablet.

Intravenous administration

Phosphate is given intravenously when hypophosphataemia is severe (<0.32mmol/L) or if patients are intolerant of or unsuitable for oral medication.

The standard dose is 9mmol of phosphate over 12hrs.

Administration

Prescribe as Phosphate polyfusor 9mmol (90 ml) over 12 hours. Administer 90ml only from a 50mmol/500ml bag by setting up the pump to run at 7.5ml/hr for 12 hours, discard the remaining solution after this time.

Monitoring

monitor blood pressure and heart rate

check calcium, potassium, other electrolytes and renal function daily

re-check phosphate the following day and repeat dose if levels <0.5mmol/L

Dosage can be increased up to 0.2 - 0.5mmol/kg of phosphate, (equivalent to 2-5mls phosphate polyfusor/kg), up to a maximum of 50mmol, may be given over 6 - 12 hours. This can be repeated if the serum phosphate remains below 0.65mmol/L.

For patients with hyperkalaemia, consider using sodium glycerophosphate. Sodium glycerophosphate (Glycophos®) contains 1mmol of phosphate and 2mmol of sodium in 1ml. This can be added to 500ml of either sodium chloride 0.9% or glucose 5% and infused over 12 hours.

Nottingham University Hospitals NHS Trust Guidelines for the treatment of acute hypophosphataemia in adults, May 2013UKMI Medicines Q&A: How is acute phosphataemia treated in adults?. Prepared 21 September 2012.

On this website you will now see four icons for these resources rather than two. Please use BNF Legacy or BNF for Children Legacy as these will take you to the original format of the online publications which do not have any errors or omissions.